DVDA on occasion does not properly write to blu-ray and I have put it down to my choice of media. My burner accepts BD-R and BD-RE discs, of which I have had zero success in getting a proper/full burn when it comes to BD-R. I at times only got the menu, or on another occasion, it only burnt about 30 minutes of playable video. I use Shintaro BD-RE discs (which are also inkjet printable) and have had a 100% burn success rate.
Try changing your blu-ray media, but make sure your burner can handle it.
My system specs: Intel i7 970, 12GB RAM, ASUS P6T, Vegas Pro 10e (x32/x64), Windows 7 x64 Ultimate, Vegas Production Assistant 1.0, VASST Ultimate S Pro 4.1, Neat Video Pro 2.6